Fluoroolefins are useful as monomers for fluoropolymers. For example, vinyl fluoride is a useful monomer for the preparation of fluorocarbon polymers which have excellent weathering and chemical resistance properties.
U.S. Pat. No. 2,599,631 discloses a process for the manufacture of vinyl fluoride by the dehydrofluorination of HFC-152a. The dehydrofluorination is done in the presence or absence of a catalyst. The dehydrofluorination catalysts disclosed include oxygen, charcoal, and the free metals, salts and oxides of the elements of Groups IA, IB, IIA, IIB, VB and VIII of the periodic table.
PCT Publication No. WO 96/05157 discloses a process for the dehydrofluorination of CH.sub.2 FCF.sub.3 to CHF.dbd.CF.sub.2 using Lewis acid catalysts. These catalysts include chromia (Cr.sub.2 O.sub.3), chromia doped with metals such as nickel, cobalt, zinc, iron and copper. Other disclosed catalysts include aluminum fluoride and materials comprising a fluorine containing Lewis acid.
CrF.sub.3 has been reported to form rhombohedral crystals (see e.g., Ullman's Encyclopedia of Industrial Chemistry, Fifth Ed., Vol. A7, p. 83). There is an ongoing interest in developing efficient catalysts for the conversion of hydrofluorocarbons to fluoroolefins.